
m 



.//3 






LIBRARY OF CONGRESS 




014 633 369 2 



.H5 



[FROM THE TRANSACTIONS OF THE AMERICAN EIJECTROCHEMICAI- 
SOCIETY, Volume XXX, 1916, being: the Transactions of the Thirtieth General 
Meeting, at New York City, September 28, 29, 30, 1916.] 



THE ELECTRODEPOSITION 
or NICKEL 



BY 

L.Df HAMMOND 

UNIVFHSITY OF WISCONSIN 

PH.D. THESIS iq/fe 






.^v 



'N 



^e>'^^ 



A paper presented at the Thirtieth Gen- 
eral Meeting of the American Electro- 
chemical Society, held in New York City, 
September 28, 1916, Mr. L. E. Saunders 
in the Chair. 



THE ELECTRODEPOSITION OF NICKEL. 

By L. D. Hammond. 

The voluminous literature on the electro-deposition of nickel 
abounds in contradictory statements concerning the conditions 
necessary for the electric current to deposit nickel from a given 
electrolyte. It also records a multiplicity of electrolytes which 
have been proposed, and testifies to the fact that the commercial 
application of the electro-deposition of nickel, commonly spoken 
of as "nickel plating," is not based upon scientific facts, but is 
an art practiced largely by those not thoroughly familiar with the 
fundamental principles of chemistry and electricity. Conse- 
quently, nickel plating, although it has been practiced for about 
fifty years, is still based upon "cut and try" methods. 

These discrepancies have been mentioned by other writers^ and 
a few examples will be cited. Langbein^ states that the nickeling 
of cooking utensils is to be discouraged on account of the solu- 
bility of nickel in hot fats, vinegar, beer, mustard, tea, etc., while 
Bouant^ states that nickel-plated utensils may be used in the 
kitchen as nickel salts do not harm the animal organism. Again, 
Langbein* states that "an alkaline reaction of nickel baths is 
absolutely detrimental," while Bennett' gives experimental data 
to show that a good deposit cannot be made from an acid electro- 
lyte. However, many laboratory experiments and commercial 
practice testify that excellent deposits are obtained from electro- 
lytes slightly acid in reaction. 

A. Brochet" is sponsor for the statement that an electrolyte 
neutral in reaction is a necessary condition to secure a good 

* Watts, Trans. Amer. Electrochem. Soc, 23, 123-147 (1913); Kalmus, Harper and 
Savelle, J. Ind. and Eng. Chem., 7, 380 (1915). 

' Electro-deposition of Metals, p. 246. 
' La Galvanoplastie, p. 186. 

* Electro-deposition of Metals, p. 319. 

•Trans. Amer. Electrochem. Soc, 25, 335-345 (1914). 
'Metal Industry, 6, 314 (1908). 



103 



/ 



I04 L. D. HAMMOND. 

deposit of nickel, while Johnson' states that "nickel must be 
deposited from an alkaline, neutral or very slightly acid electro- 
lyte." However, commercial practice in plating shows the neces- 
sity for maintaining the bath slightly acid. This condition is 
usually accomplished by the addition of boric acid, and, although 
its use for this purpose is very general, the function of boric acid 
in the electrolyte has never been explained.* This point will be 
discussed in detail later. 

Again, Bennett^ states that those electrolytes to which ammo- 
nium hydroxide was added "always gave a more adherent and 
better deposit" while the Brass World^^ in an article entitled "The 
Effect of Ammonium Hydroxide on Nickel Plating Solutions" 
finds that its presence is detrimental to a good deposit. Also the 
same journal,^ ^ as well as Hogaboom,^^ finds that copper salts 
in the electrolyte have a bad effect upon the nickel deposit, while 
Brown^^ states that copper in the anode is beneficial in that it in- 
creases anode corrosion. Bancroft" condemns the presence of 
iron in the plating bath to which presence he attributes the rust- 
ing of nickel plated articles, while the Brass World^^ says "at 
one time the presence of iron in the nickel deposit was looked 
upon as a very serious matter, but lately it not only has been 
looked upon less gravely, but in many instances is actually con- 
sidered beneficial, particularly for certain kinds of work. Iron 
hardens the nickel when it is present in the deposit, and also pro- 
duces a whiter color. To be sure, nickel containing a small quan- 
tity of iron tarnishes more readily, but even so it does not rust, 
but is subject only to the tarnish, which is not a serious matter 
on many classes of work." 

Many of the earlier electrolytes proposed for nickel plating 
contained five or six different substances dissolved in water, but 
Watts^* has stated that baths of simpler composition are to be 
preferred, and experiments recorded in this paper lead to the 
same conclusion. However, all of the unnecessarily complex 

'Trans. Amer. Electrochem. Soc, 3, 255 (1903). 

' lyangbein, Electro-deposition of Metals (1909), p. 249, and Trans. Amer. Electro- 
chem. Soc, 27, 118 (191S). 

» Trans. Amer. Electrochem. Soc, 25, 341 (1914). 

'"Brass World, 7, 137 (1911). 

"Brass World, 7, 45 (1911). 

"Trans. Amer. Electrochem. Soc, 23, 269 (1913). 

"Trans. Amer. Electrochem. Soc, 4, 83 (1903). 

"Trans. Amer.. Electrochem. Soc, 9, 218 (1906). 

"Brass World, 7, 154 (1911). 

"Trans. Amer. Electrochem. Soc, 23, 118 (1913). 



Gin 



THE ET^ECTRODEPOSITION OF NICKEL. 105 

baths have not been proposed in the past, as quite recently 
Mathers^^ has proposed one of this type, which will be discussed 
in detail later. Although several baths containing nothing but a 
nickel salt dissolved in water have been proposed,^* Yates,^® 
Powell,'^ and the Brass IVorld-^ maintain that single salts cannot 
be used in plating. Brochet'-- states that, in order to secure a 
good deposit, a mixture of nickel sulphate and the chloride to 
which must be added an alkali salt is required, but it will be shown 
later that a good deposit can be obtained from nickel sulphate dis- 
solved in water acidified with a small amount of hydrochloric 
acid. This solution contains all the factors necessary for a good 
deposit, so far as the electrolyte is concerned. Watts^^ has called 
attention to and criticized the statement of Sackur-* that "good 
nickeling depends only on the choice of the right E. M. F., not 
upon the composition of the bath." 

It has long been known that nickel anodes do not corrode satis- 
factorily and several methods have been proposed to overcome 
this difficulty. Brown-^ has measured the efficiency of anode cor- 
rosion in nickel-ammonium sulphate solution using anodes of 
electrolytic, rolled, and cast nickel. Cast anodes gave the highest 
efficiency, due to the impurities present, while the pure rolled 
anodes showed a very low efficiency. So commercial practice has 
sanctioned the addition of iron, carbon, and tin up to eight per- 
cent to overcome this so-called passivity of the nickel anode. 
Brown-® approves of such practice while Bancroft-^ ascribes the 
rusting of nickel-plated objects to the presence of iron in the 
anode, which dissolves and deposits with the nickel, thus causing 
rusting. To avoid the rusting of nickel-plated objects, he pro- 
poses the use of pure nickel anodes and to induce good anode 
corrosion by the addition of ammonium chloride or nickel chloride 
to the electrolyte. Sodium chloride and magnesium chloride have 
also been proposed and used. 

"Trans. Amer. Electrochem. Soc, 29, Apr., 1916. 

" Watts, Trans. Amer. Electrochem. Soc, 23, 124-125 (1913). 

i» Trans. Amer. Electrochem. Soc, 23, 118 (1913). 

» U. S. Patent, 229274, June 29, 1880. 

=1 Brass World. 3, 129 (1907). 

^^2 Manual Pratique de Galvanoplastie (1908), p. 229. 

"Trans. Amer. Electrochem. Soc, 23, 119 (1913). 

" Elektrometallurgie, Peters, 4, 155. 

"Trans. Amer. Electrochem. Soc, 4, 87 (1903). 

"Trans. Amer. Electrochem. Soc, 4, 86 (1903). 

^ Trans. Amer. Electrochem. Soc, 9, 218 (1906). 



I06 I,. D. HAMMOND. 

Although Adams'^ states that "the art (of nickel plating) is 
today carried on substantially as it was in 1869-70, with the same 
solutions, the same anodes and the same details of shop manipu- 
lation," and although Foster-^ says that the trend of all improve- 
ment in nickel plating has been along mechanical lines, there has 
been a noticeable tendency to break away from the commonly 
used electrolyte, which consists chiefly of nickel ammonium sul- 
phate. This has resulted from the introduction of the so-called 
"high power" or "rapid" plating solutions which, on account of 
their greater concentration of nickel salt, secured by the substi- 
tution of nickel sulphate for the less soluble nickel ammonium 
sulphate, permit a higher current density to be employed. These 
"high power" salts generally contain boric acid together with a 
chloride to insure anode corrosion. The most notable advance 
along this line has been the proposal of Watts^° to use a concen- 
trated solution of nickel sulphate to which is added nickel chloride 
and boric acid and to heat the bath to 70°. In this electrolyte, 
plating has been done at the current density of thirty-three am- 
peres per square decimeter. 

In view of these conflicting statements concerning the condi- 
tions best suited to the electro-deposition of nickel, the temptation 
was very great, both to inquire into them and to investigate some 
of the "rule of thumb" methods which have grown up with the 
plating industry. This paper reports the results of experiments 
made upon the corrosion of electrolytic nickel anodes, annealed 
electrolytic nickel anodes, and cast nickel anodes in various elec- 
trolytes ; upon the conditions necessary for the direct deposition 
of nickel on zinc ; and upon the use of boric acid in the electrolytes 
with the view of explaining its function. 

I. ANODE CORROSION. 

One of the important factors in the successful operation of a 
plating bath is the manner in which the anode corrodes. Under 
ideal conditions, nickel would dissolve at the anode at the same 
rate at which it is deposited at the cathode, and the composition 
of the bath would not be changed. If the rate of the solution at 

=8 Trans. Amer. Electrochem. Soc., 9, 215 (1906). 

2» Metal Industry, 6, 8 (1908). 

'"Trans. Amer. Electrochem. Soc, 29, 395 (1916). 



THi; ELEICTRODEPOSITION OP NICKEI.. IO7 

the anode is smaller than the rate of deposition at the cathode, 
the composition of the electrolyte will change, as its nickel con- 
tent will decrease and the acid content increase. On the other 
hand, if the anode dissolves faster than the rate of deposition at 
the cathode, the nickel concentration of the electrolyte will in- 
crease and it will become alkaline in reaction. It has long been 
known that, when anodes of pure nickel are used, they soon fail 
to corrode properly and behave as the noble metals. This so- 
called passivity of the anode is remedied by substituting cast nickel 
anodes for the purer metals. An analysis of commercial anodes 
by Calhane and Gammage^^ showed about 7.5 percent of iron, 
and the metal deposited from these anodes contained from 0.07 
to 0.75 percent of iron. The Brass WorlcP^ states that impuri- 
ties consisting of iron, tin and carbon "are introduced intention- 
ally to render the anode 'soft,' i. e., so that it will dissolve easily 
in the solution during plating." Although solution of anode is 
promoted by such practice, serious troubles result. The presence 
of the iron, tin, and carbon doubtless causes the anode to corrode 
on open circuit due to voltaic action. The more serious trouble, 
however, results from the fact that some iron is deposited along 
with the nickel, and the nickel plated object is coated, eventually, 
with rust. 

Since the only kind of anodes obtainable are those containing 
iron, carbon, and tin, it was considered worth while to study the 
corrosion of electrolytic nickel in various electrolytes. Because 
the only electrolytic nickel available consists of rather thin sheets, 
some anodes were prepared by melting the electrolytic nickel and 
casting into bars 20 X 4 X 0.8 cm. A second anode was pre- 
pared by taking a piece of the electrolytic nickel 17 X 4.5 X 0.3 
cm. and annealing it. The third was simply a piece of the 
electrolytic nickel 20 X 4.5 X 0.2 cm. , These anodes will be re- 
ferred to as the cast, annealed, and electrolytic anodes respectively. 

Brown ^^ has pointed out the relation existing between the cur- 
rent efficiency of anode corrosion and the anode discharge poten- 
tial in an electrolyte of nickel-ammonium sulphate, and it was 
deemed worth while to study anode corrosion in more modern 
electrolytes. The method of anode discharge potentials was not 

"J. Amer. Chem. Soc, 29, 1268 (1907). 

=2 Brass World, 7, 154 (1911). 

'■■'Trans. Amer. Electrochem. Soc, 4, 94 (1903). 



io8 



L. D. HAMMOND. 



employed, but advantage was taken of the -fact, pointed out by 
Brown^^ that "a study of total polarization pressure, while not 
being as definite in the indications as a study of the individual 
electromotive force at the electrodes, will serve as a means for 
determining whether the cell is operating properly. When the 
polarization goes much above 0.75 volt, the assumption is justified 
that the anode is not corroding properly, and, on the other hand, if 
the polarization is below 0.7 volt, the efficiency at the anode is 
as high as can be obtained." Three different kinds of anodes were 
selected for this study as stated above. All of these anodes were 
prepared for the electrolyte by being scrubbed with powdered 
pumice, rinsed in cold water, subjected to the action of the electric 
cleaner for about ten seconds, rinsed in hot water and finally in 
cold. In all measurements the cathodes employed were of copper 
cleaned by being buffed, placed in the electric cleaner for about 
ten seconds and rinsed, first in hot, and then in cold water. The 
electrodes were then placed in the given electrolyte and the total 
polarization pressure at various current densities was read. In 
all cases the measurements were made at room temperature. All 
current densities are reported in amperes per square decimeter. 



Table I. 

Electrolyte: 120 gm. NiS04.6H20 per liter. 



Amp. 


Current Density 


E. 


M. F. Volts 


Polarization Volts 




Cast. 


Elec. 


Anneal. 


Cast. 


Elec. 


Anneal. 


Cast. 


Elec. 


Anneal. 


0.05 


0.20 


0.228 


0.237 


2.20 


2.60 


1.20 


0.40 


2.00 


0.40 


0.10 


0.40 


0.45 


0.47 


3.00 


3.20 


1.75 


0.40 


2.00 


0.40 


0.25 


1.00 


1.14 


1.18 


4.40 


4.65 


4.30 


0.45 


2.00 


0.90 


0.50 


2.00 


2.28 


2.36 


7.50 


7.50 


7.50 


0.50 


2.00 


1.20 


1.00 


4.00 


4.56 


4.72 


11.25 


12.50 


12.50 


0.50 


2.00 


1.70 


2.00 


8.00 


9.12 


9.44 


18.50 


19.50 


21.00 


0.60 


2.00 


2.00 


3.00 


12.00 


13.68 


14.16 


22.25 


22.40 




0.60 


2.00 




4.00 


16.00 


18.24 


18.88 


26.25 


27.00 


28.00 


0.60 


2.00 


2.66 



Table I. — At 12 amp. per sq. dm. the temperature had risen to 
42° while at 16 it was 65°. The cathodes began to gas freely at 
a current density of 1 amp. The cast anode evolved gas at 8 amp. 
per sq. dm., while the first evolution of gas at the other two was 
noted at about 5 amp. All these cathodes gassed freely at the 
same rate. The electrolytic and annealed anodes evolved gas 



THE EI.ECTRODEPOSITION OF NICKEL. 



109 



freely, although not so rapidly as the cathodes, while the cast 
anode gassed at about half the rate of the other anodes. The 
electrolyte in which the cast anode was immersed became turbid 
and alkaline in reaction, while the others remained clear but be- 
came acid in reaction. The cast anode was slightly brownish 
black while the other two were metallic in appearance. All anodes 
showed signs of pitting. The cathodes were black at first, but 
at the higher current densities became covered with a green salt. 
The data in Table I show that in an electrolyte containing only 
nickel sulphate dissolved in water, the cast anode corrodes satis- 
factorily, although it is less efficient at the higher current densi- 
ties. The electrolytic anode corrodes very poorly from the start, 
while the effect of annealing is shown only at the lower densities. 
As the current density is increased the corrosion decreases, until 
finally this anode behaves as the unannealed one. 

Table II. 
Electrolyte: NiS0..6H=0 120 gm. and H,BO» 30 gm. per liter. 



Amp. 


Current Der 


sity 


E. 
Cast. 


M. F. Volts 


Polari 


zation Volts 




Cast. Elec. 


Anneal. 


Elec. 


Anneal. 


Cast. 


Elec. 


Anneal. 


0.05 


0.20 0.228 


0.237 


1.50 


2.20 


1.40 


0.3 


1.20 


0.3 


0.10 


0.40 0.45 


0.47 


1.80 


3.25 


1.70 


0.3 


1.80 


0.3 


0.25 


1.00 1.14 


1.18 


3.25 


4.82 


3.20 


0.3 


1.80 


0.3 


0.50 


2.00 2.28 


2.36 


6.25 


7.50 


6.00 


0.3 


1.80 


0.3 


1.00 


4.00 4.56 


4.72 


10.00 


10.70 


11.50 


0.3 


1.80 


0.3 


2.00 


8.00 9.12 


9.44 


14.75 


14.50 




0.3 


1.50 




3.00 


12.00 13.68 


14.16 


21.00 


19.50 




0.3 


1.40 




4.00 


16.00 18.24 


18.88 


23.60 


22.50 




0.3 


1.30 





Table II. — At about 8 amp. per sq. dm. the electrolytic and an- 
nealed anodes were gassing freely, while the cathodes were 
evolving gas but feebly at twice that current strength. At the 
cast anode a few bubbles were occasionally seen. The electro- 
lytic and annealed anodes were bright, and the cast anode was 
black around the pitted portions, although otherwise bright. The 
electrolytes were clear, with the exception of that of the cast 
anode, which was turbid. 

The data in Table II show that in the boric acid solution the 
corrosion of the cast and annealed anodes is very satisfactory. 
At the lowest current densities the electrolytic anode corrodes 



no 



h. D. HAMMOND. 



slightly better than in the previous electrolyte. As the current 
strength is increased this anode becomes more passive, but at the 
highest current densities the corrosion is the same as at the lowest 
current densities. 

Table; III. 

Electrolyte : 
NiSOi.eH^O 120 gm.; H3BO3 30 gm. ; NiCU.aHaO 5 gm. per liter. 



Amp. 


Current Density 


E. M. F. Volts 


Polarization Volts 




Cast. 


Elec. 


Anneal. 


Cast. Elec. 


Anneal. 


Cast. 


Elec. 


Anneal. 


0.05 


0.20 


0.228 


0.237 


1.10 2.25 


1.00 


0.20 


1.20 


0.20 


0.10 


0.40 


0.45 


0.47 


1.65 3.08 


1.35 


0.20 


1.60 


0.20 


0.25 


1.00 


1.14 


1.18 


2.70 4.60 


2.45 


0.20 


1.70 


0.20 


0.50 


2.00 


2.28 


2.36 


5.70 7.00 


4.25 


0.20 


1.50 


0.15 


1.00 


4.00 


4.56 


4.72 


14.00 12.00 


8.00 


0.40 


1.50 


0.10 


2.00 


8.00 


9.12 


9.44 


19.75 20.50 


15.00 


0.50 


1.50 


0.20 


3.00 




13.68 


14.16 


.... 28.50 


22.50 




1.80 


0.30 



Table III. — At a current density of 12 amp. the temperature 
rose to 30°. At 5 amp. the cathodes began to evolve gas and as 
the current density became greater the gas evolution correspond- 
ingly increased. At about 2 amp. the anodes began to liberate gas. 

The data in Table III show that nickel chloride to the extent 
of 5 gm. per liter causes marked corrosion of both the cast and 
annealed anodes as was to be expected, and, although at the lowest 
current densities the corrosion of the electrolytic anode was im- 
proved, its behavior was still unsatisfactory. 



TABI.E IV. 

Electrolyte : 

NiS04.6H20 120 gm.; H3BO3 30 gm. ; NiCU.eHzO 10 gm. per liter. 



Amp. 


Current Den 


sity 


E. M. F. Volts 


Polarization Volts 




Cast. 


Elec. 


Anneal. 


Cast. Elec. 


Anneal. 


Cast. 


Elec. 


Anneal. 


0.05 


0.20 


0.228 


0.237 


1.05 2.08 


1.30 


0.20 


1.20 


0.2 


0.10 


0.40 


0.45 


0.47 


1.60 3.15 


1.55 


0.20 


1.20 


0.2 


0.25 


1.00 


1.14 


1.18 


3.00 4.80 


2.90 


0.20 


1.20 


0.2 


0.50 


2.00 


2.28 


2.36 


5.40 7.50 


5.10 


0.20 


1.20 


0.2 


1.00 


4.00 


4.56 


4.72 


10.75 12.40 


9.00 


0.45 


1.20 


0.2' 


2.00 


8.00 


9.12 


9.44 


20.25 20.00 


17.10 


0.50 


1.20 


0.2 


3.00 


12.00 


13.68 


14.16 


27.50 29.00 


25.00 


0.50 


1.40 


0.3 



THE e;i,ectrodeposition of nickel. 



Table IV. — At 12 amp. per sq. dm. the temperature rose to 28°. 
Table IV shows that the addition of nickel chloride to the con- 
centration of 10 gm. per liter materially increases the corrosion 
of the electrolytic anode, although it still does not corrode satis- 
factorily. 

Table V. 

Electrolyte : 
NiS04.6H20 120 gm. ; H3BO3 30 gm.; NiCU.eH.O 15 gm. per liter. 



Amp. 


Current Density 


E. M. F. Volts 


Polarization 


Volts 




Cast. 


Elec. 


Anneal. 


Cast. Elec. 


Anneal. 


Cast. 


Elec. 


Anneal. 


0.05 


0.20 


0.228 


0.237 


1.05 1.15 


1.20 


0.20 


0.2 


0.2 


0.10 


0.40 


0.45 


0.47 


1.40 1.60 


1.40 


0.50 


0.3 


0.2 


0.25 


1.00 


1.14 


1.18 


2.64 3.50 


2.80 


0.50 


0.4 


0.2 


0.50 


2.00 


2.28 


2.36 


4.75 6.50 


4.50 


0.45 


0.4 


0.2 


1.00 


4.00 


4.56 


4.72 


8.75 11.00 


7.75 


0.45 


0.5 


0.2 


2.00 


8.00 


9.12 


9.44 


15.00 17.50 


16.00 


0.45 


0.6 


0.25 


3.00 


12.00 


13.68 


14.16 


20.50 25.00 


23.00 


0.50 


0.7 


0.30 


4.00 


16.00 


18.24 


18.88 


24.75 .... 




0.50 


•• 





Table V. — At 12 amp. per sq. dm. the temperature rose to 36°, 
and at 16 amp. it was 40°. At 5 amp. there was a slight gassing 
at both cathodes and at the electrolytic and annealed anodes. The 
electrolyte of the cast anode was turbid and alkaline, and, upon 
standing, nickelous hydroxide precipitated. The other electro- 
lytes were clear and acid in reaction. The anodes were bright and 
slightly pitted. 

The data of Table V show that with a concentration of nickel 
chloride at 15 gm. per liter the electrolytic anode corrodes very 
well. 

Table VI. 

NiS04.6H20 120 gm.; H3BO3 30 gm. ; NiCU.eH^O 30 gm. per liter. 



Amp. 


Current Der 


isity 


E. 


M. F. Volts 


Polarization 


Volts 




Cast. 


Elec. 


Anneal. 


Cast. 


Elec. 


Anneal. 


Cast. 


Elec. 


Anneal. 


0.05 


0.20 


0.228 


0.237 


0.95 


1.00 


1.05 


0.2 


0.2 


0.15 


0.10 


0.40 


0.45 


0.47 


1.40 


1.45 


1.30 


0.2 


0.2 


O.IS 


0.25 


1.00 


1.14 


1.18 


2.65 


3.00 


2.20 


0.2 


0.4 


0.15 


0.50 


2.00 


2.28 


2.36 


4.45 


5.00 


4.25 


0.2 


0.4 


0.10 


1.00 


4.00 


4.56 


4.72 


8.50 


9.50 


7.00 


0.2 


0.4 


0.10 


2.00 




9.12 


9.44 




16.50 


13.00 




0.4 


0.10 


3.00 




13.68 


14.16 




23.00 


19.00 




0.5 


0.15 


4.00 




18.24 


18.88 




28.50 


23.25 




0.7 


0.20 



112 



L. D. HAMMOND. 



Table VI. — At 5 amp. per sq. dm. the temperature rose to 29°, 
while at 16 amp. it was 35°. Gas was evolved at all electrodes 
except the annealed anode. When removed from the electrolyte 
the anodes were all bright. As is to be expected, all anodes cor- 
rode well. Both the cast and annealed show better corrosion than 
in the previous electrolytes, but doubling the concentration of the 
nickel chloride does not materially change the corrosion of the 
electrolytic anode. 

In Table VII are given the results of measurements of total 
polarization pressures, using an electrolytic nickel anode and 
copper cathode in an electrolyte of 40 gm. of nickel sulphate per 
liter, to which progressive additions of nickel chloride were made. 

Table VII. 



Grams per Liter 


Amp. 


Current 


E. M. F. 


Polarization 


of Nidj.eHgO 


Density 

0.20 


Volts 


Volts 





0.1 


2.80 


2.00 


1 


0.1 


0.20 


2.80 


1.70 


2 


0.1 


0.20 


2.75 


1.60 


4 


0.1 


0.20 


2.68 


1.30 


6 


0.1 


0.20 


1.78 


0.60 



From Table VII it will be seen that 6 gm. per liter of nickel 
chloride are required as the minimum amount necessary to pro- 
duce fair corrosion, although 15 gm. per liter (Table V) are 
necessary to secure the best results. 

In Table VIII are given the results of current efficiency meas- 
urements with the anodes and electrolytes used in making the 
total polarization pressure measurements. Copper cathodes were 
used in all cases and their efficiencies were also measured. 



Electrolyte, 
gm. per liter 



NISO4.6H2O 120. 

NiS04.6H20 120. 

H3BO3 30.. 

NiS0..6H.O 120. 

H3BO3 30.. 

NiCU.6H20 10.. 



Table VIII. 








CD. 


Current Efficiency 


Cast Anode 
Corr. Dep. 


Elec. 
Corr. 


Anode 
Dep. 


Annealed Anode 
Corr. Dep. 


0.5 


107.4 58.32 


38.50 


42.53 


74.30 42.94 


[ 0.5 


97.57 96.31 


45.81 


47.23 


102.80 97.47 


1 0.5 


96.25 94.98 


98.52 


97.45 


109.1 98.16 



THE ELECTRODEPOSITION OE NICKEL. II3 

Table VIII. — These figures confirm in a quantitative manner 
the indications of anode corrosion shown by the total polarization 
pressures. This study of anode corrosion shows that, although 
cast anodes corrode fairly well in the simple sulphate electrolytes 
to which boric acid has been added, the best practice is to use the 
purest electrolytic nickel and to use nickel chloride to secure good 
corrosion. Nickel chloride is to be preferred to other chlorides, 
as its addition does not decrease the concentration of nickel in 
the electrolyte. It has been shown that 6 gm. per liter of nickel 
chloride will produce good anode corrosion, and that the best 
results are secured by increasing the nickel chloride to 15 gm. 
per liter. 

II. THE DIRECT NICKELING OF ZINC. 

Attention is being attracted to the direct deposition of nickel 
on zinc owing to the increased use of zinc to cover tables, kitchen 
cabinets, etc., and to its use in die castings, which are largely zinc. 
Langbein^* states that "sheet zinc directly nickeled does not show 
the warm, full tone of sheets previously coppered or brassed. 
The nickel deposit on brassed sheets shows a decidedly whiter 
tone than on copper sheets, and brassing would deserve the pref- 
erence if this process did not require extraordinarily great care 
in the proper treatment of the bath, the nickel deposit readily peel- 
ing off." Experiment has shown that all of the baths proposed 
for the direct nickeling of zinc give a deposit of yellowish nickel, 
but that this can be remedied by the addition of acid to the bath. 

The direct nickeling of zinc presents difficulties not encountered 
in the deposition of nickel upon copper or brass, due to the fact 
that zinc is more electro-positive than nickel, so that, when the 
zinc is placed in the electrolyte, a non-adherent deposit of black 
nickel immediately appears, which causes the metal, afterward 
deposited on the zinc by the current, to peel. In order to avoid 
the trouble caused by this deposition by immersion two methods 
are in use at present. One is to coat the zinc first with a more 
negative metal or alloy, such as copper or brass, w^hich can be 
done in an electrolyte containing potassium cyanide, since the 
copper or brass becomes more positive in such a solution, and the 
difference between the single potentials of zinc and copper is so 

^* Electro-deposition of Metals, p. 298. 

8 



114 



h. D. HAMMOND. 



small that deposition by immersion does not occur. However, this 
method involves a second operation which, from a commercial 
viewpoint, makes the process more expensive. The second 
method is to subject the article to be plated for about thirty sec- 
onds to an initial current density much higher than that regularly 
employed. This is called "striking." 

In looking over the electrolytes that have been proposed^^ for 
the direct nickeling of zinc, it is seen that they are all low in nickel 
content, which permits only a small current density to be em- 
ployed, and that other substances have been added, such as mag- 
nesium sulphate, potassium or sodium citrate, phosphates, bisul- 
phites, etc., which are for the purpose of making the zinc less 
positive to the electrolyte. It is the object of this part of the 
paper to report the results of study made first, to find out the 
purpose of these added substances ; second, to see if they make 
the zinc less positive ; and, third, to see if nickel cannot be directly 
deposited more rapidly than from the baths already proposed. 

To see if there was any change in the relative potentials of the 
zinc and nickel it was decided to measure their potentials in the 
various baths proposed for the direct nickeling of zinc. The 
Poggendorf compensation method was employed together with 
the normal calomel electrode, the potential of which was taken 
as — 0.56 volt. The measurements were all made at room 
temperature. 

Table IX. 



Electrolyte 



Nickel sulphate 40 gm. 

Sodium citrate 35 gm. 

Water 1000 cc. 

Same electrolyte 

Nickel ammonium sulphate 56 gm. 

Magnesium sulphate 26 gm. 

Water 1000 cc. 

Same electrolyte 

Ammonium chloride 37.5 gm. 

Nickel chloride 37.5 gm. 

Water 1000 cc. 

Same electrolyte 



Metal 



Single Potential 



Ni 
Zn 
Ni 
Zn 
Ni 
Zn 



0.205 

0.55 

0.20 

0.498 

0.28 

0.51 



••Watts, Trans. Amer. Electrochem. See, 23, 149 (1913). 



THE EI.ECTRODEPOSITION OF NICKEI,. II5 

Table IX shows that, in the baths proposed for the direct nickel- 
ing of zinc, the single potentials of both nickel and zinc have prac- 
tically the same values as in normal solutions of their salts. The 
zinc is not less positive in these baths and should precipitate nickel 
by immersion. In all these baths it was found that such was the 
case. It will be shown later that sodium citrate slows down the 
rate with which the deposition by immersion takes place, and it 
is to this effect that its beneficial action is due. 

Several of the baths which have been proposed for the direct 
nickeling of zinc were prepared and tested. Of those tried only 
one proved satisfactory. This was the one proposed by Pfan- 
hauser,^" consisting of 40 gm. of nickel sulphate and 35 gm. of 
sodium citrate per liter. At a current density of 0.5 amp. and 
E. M. F. of 2.7 volts the total polarization pressure was 1.8 volts, 
indicating very poor anode corrosion, which was to be expected 
from the absence of any chloride. The deposit, however, was 
adherent and of a yellowish tint. Similar baths proposed by 
Langbein^'^ and by Proctor^^ contain potassium citrate and ammo- 
nium chloride and should give good deposits. All these baths are 
low in nickel content and so can be operated only at small current 
densities. Since the rate of deposition by immersion increases 
with the increase of the concentration of nickel salt, it is not 
surprising that these dilute solutions were used. However, more 
concentrated solutions have been successfully employed, as will 
be shown later. 

Two other baths proposed by Langbein^^ were prepared and 
tried, but they did not yield good deposits. One contained 56 
gm. of nickel-ammonium sulphate and 26 gm. of magnesium sul- 
phate per liter, while the other contained Z7 gm. each of nickel 
chloride and ammonium chloride per liter. The bath proposed 
by Proctor in the Metal Indiistry^^ gives satisfactory deposits, 
but, as will be shown later, it contains unnecessary components 
and in its stead a simpler bath is proposed. 

It was noted, in the baths proposed for the direct nickeling of 
zinc, that if a piece of zinc were immersed in the electrolyte, it 
would finally be coated by immersion ; therefore, it was decided 

" Elektroplattirung, W. Pfanhauser (1900). 
•'Electro-deposition of Metals, p. 319 (1909). 
•'Metal Industry, 9, 353 (1911). 
»» Metal Industry, 13, 274 (1915). 



Il6 L. D. HAMMOND. 

to determine how the rate of deposition by immersion was affected 
by changes of temperature. For this purpose a bath proposed by 
Pfanhauser*" was chosen which had the following composition: 

Nickel sulphate 40 gm 

Sodium citrate 35 gm. 

Water 1000 cc. 

Strips of zinc were polished, cleaned in the electric cleaner, im- 
mersed in the electrolyte, and the temperature, time and the char- 
acter of the deposit noted. 







TabIvE X. 




Temp. 


Time 


Deposit 




0° 


15 mill. 


None. 




0° 


30 mill. 


None. 




0° 


45 mill. 


Slight coloration. 




18.5° 


15 mill. 


Slight coloration, hardly as much as 


above 


18.5° 


30 mill. 


Decided yellow color. 




18.5° 


45 min. 


Black brown. 




45° 


10 sec. 


None. 




45° 


30 sec. 


Perceptible color of yellow. 




45° 


60 sec. 


Decided yellow. 




60° 


10 sec. 


Perceptible yellow. 




60° 


20 sec. 


Yellow. 




60° 


30 sec. 


Decided yellow. 




75° 


10 sec. 


More than perceptible. 




75° 


20 sec. 


Decided yellow. 




75° 


30 sec. 


Brownish black. 




90° 


5 sec. 


Decidedly perceptible. 




90° 


10 sec. 


Yellow. 




90° 


15 sec. 


Brown. 




90° 


20 sec. 


Blue black. 





The data of Table X show why hot solutions, which have been 
so advantageously employed in nickeling copper, for example, 
cannot be used in the direct deposition of nickel on zinc, since the 
rate of deposition by immersion increases with increase of tetn- 
perature. Experience has also shown that this rate, even at ordi- 
nary temperature, is increased with the increase of concentration 
of nickel salt in the electrolyte. This fact explains why all the 
baths proposed for the direct nickeling of zinc are low in nickel. 

In examining the conditions necessary for the direct deposition 
of nickel on zinc, the following data show the relation between 
the character of the deposit and the composition of the electrolyte 
and current density employed. Twenty different electrolytes were 

*' Elektroplattirung, W. Pfanhauser, 1900. 



TIIK EI<ECTR0DEP0SITI0N OF NICKEL. 1 17 

Studied, in which the nickel sulphate varied in concentration from 
40 gm. per liter to a saturated solution. Some of these were used 
without the addition of any other substance, while in other solu- 
tions nickel chloride was added. Still others contained varying 
amounts of nickel sulphate and nickel chloride acidified separately 
with various acids. The current density varied all the way from 
0.2 amp. to 15 amp. per square decimeter. These experiments 
show that nickel can be deposited directly on zinc from an electro- 
lyte of any concentration of nickel which is acid in reaction and 
contains nickel chloride to secure proper anode corrosion. It is 
only necessary to vary the cvirrent density employed, which must 
be increased as the concentration of nickel increases. It is not 
absolutely necessary to add sodium citrate or magnesium sulphate 
to the electrolyte, although the presence of the former is advanta- 
geous, as will be discussed later. 

Langbein^^ states that the bath for the direct nickeling of zinc 
containing citrate must be kept strictly neutral, but experiment 
has shown this statement to be untrue. The bath proposed by 
Pfanhauser*' consisting of nickel sulphate 40 gm. and sodium 
citrate 35 gm. per liter was prepared and a strip of zinc was plated 
at 0.27 amp., the current density recommended. The deposit was 
metallic and adherent, but of a dark yellow tint. The current 
density was increased to one ampere with no change in the char- 
acter of the metal deposited. Boric acid to the extent of 30 gm. 
per liter was added, and at 1 amp. a fine deposit was obtained 
of much lighter shade than before. However, there was a total 
polarization pressure of 1.8 volts showing that the anode was not 
corroding properly. Upon adding nickel chloride to a concentra- 
tion of 10 gm. per liter, the character of the deposit was not 
changed, but the total polarization value of 0.5 volt showed that 
the anode was corroding properly. Thus by adding acid to Pfan- 
hauser's bath, a whiter nickel is produced, and the addition of 
nickel chloride permits the bath to be operated at a current den- 
sity four times that of the original bath and with a smaller con- 
sumption of power. 

Table XI shows the effect of the addition of sodium citrate to 
the baths for the direct nickeling of zinc. 

^^ Langbein, Electro-deposition of Metals, p. 151. 
" Electroplattirung, W. Pfanhauser (1900). 



ii8 



I.. D. HAMMOND. 



Tabi,e XI. 



Electrolyte, 
gm. per liter 



NiS04.6H20 

NiCl2.6HjO 

H3BO3 

NiS04.6H20 

NiCU.eHsO 

H3BO3 



NiS04.6H=0 

NiCI:.6H20 

H3BO3 



NiSOi.eH^O 

NiCl3.6H20 

H3BO3 

NaaCeHsOr 

NiS04.6H20 
NiCla.6H20 
H3BO3 
NajCeHoOT 



NiS04.6H20 

NiCU.6H20 

H3BO3 



NiS04.6H=0 

NiCU.eHaO 

H3BO3 

NaoCeHsOr 

NiS04.6H20 
NiCU.6H20 
H3BO3 
NasaHsOr 

NiS04.6H20 
NiCU.6H20 
H3BO3 
NasCeHsOT 



NiS04.6H20 
NiCU.eHjO 
H3BO3 
NaaCsHsO: 



40] 

10 
30 J 

55] 
10^ 
30) 



120"', 
101- 
30 j 

1201 
10, 

30! 

35' 

1201 
10 I 
30 i 
70 J 



240] 
10 ^ 
30 I 



240 I 
10 I 
30 i 
70 J 

2401 
10 [ 
30 ( 

105) 

2401 

10 

30 
140 



240] 
10! 
30 

175] 



Amp. 


CD. 

1 


E. M. F. 
Volts 


1 Polar- 
ization 
1 Volts 


0.10 


1. 00 


2.60 


0.6 


0.10 


1.00 


■ 2.50 


0.6 


0.10 
0.20 
0.30 


1.00 
2.00 
3.00 


2.20 
3.20 
4.58 


0.6 
0.6 
0.6 


0.40 


4.00 


5.60 


0.6 


0.10 
0.20 
0.30 


1.00 
2.00 
3.00 


1.80 
3.20 
4.10 


0.6 
0.6 
0.6 


0.10 
0.20 


1.00 
2.00 


2.80 
3.50 


0.6 
0.6 


0.10 
0.20 
0.30 
0.40 
0.50 


1.00 
2.00 
3.00 
4.00 
5.00 


2.60 
3.20 
3.60 
4.00 
4.75 


0.8 
0.8 
0.8 
0.8 
0.8 


0.60 


6.00 


5.20 


0.8 


0.10 
0.20 
0.30 


1.00 
2.00 
3.00 


2.70 
3.25 
3.70 


0.6 
0.6 
0.6 


0.10 
0.20 
0.30 


1.00 
2.00 
3.00 


2.80 
3.25 
3.85 


0.5 
0.5 
0.5 


0.10 
0.20 
0.30 


1.00 
2.00 
3.00 


2.75 
3.20 
3.72 


0.5 
0.5 
0.5 


0.05 
0.10 
0.20 
0.40 


0.50 
1.00 
2.00 
4.00 


2.50 
2.75 
3.30 
3.90 


0.5 
0.5 
0.5 
0.5 


0.60 


6.00 


5.05 


0.5 


0.70 


7.00 


5.30 


0.5 



Deposit 



Yellow, adherent. 



Yellow, adherent. 

White streaks, polished yellow. 

Not so streaked. 

Matte, polished well. This is 
as good a deposit as the 
modified Pfanhauser bath. 

Unsatisfactory. 

Black. 
Good. 
Matte, polished well. 



Good. 
Matte, fine. 

Brown streaks. 
Brown streaks, but not so many. 
Brown streaks, but still less. 
Matte, few brown streaks. 
Matte, polished bright around 

edges, but dull in middle 

area. 
Matte, polished well. 

Slightly streaked. 
Matte, except few areas. 
Matte, fine. 

Brown lines. 
Matte, fine. 
Matte, fine. 

Small areas of irreg. dep. 
Good. Slight irreg. in center. 

Matte, fine. 

Bright, fine. 

Bright, fine. 

Slightly matte, fine. 

5 min. dep. curled on edges ; 

2 min. dep. fine. 
2 min. dep. burned on edges ; 

1 min. dep. fine. 
1 min. dep. fine. 



THE EI^ECTRODEPOSITION OF NICKEL. 



119 



Table XI brings out very clearly the efifect of the sodium citrate 
on the bath for the direct deposition of nickel on zinc. In the 
first place, it is demonstrated that sodium citrate is not necessary 
for a good deposit of nickel directly on zinc. With a small con- 
centration of nickel good deposits are made at a current density 
of 1 ampere, which is four times the rate employed in Pfan- 
hauser's bath. As the concentration of nickel sulphate was in- 
creased to 120 gm. per liter, the current density required to secure 
a good deposit was 3 amp. per square decimeter. This deposit 
was excellent, and was as good as the one obtained by adding 
nickel chloride and boric acid to Pfanhauser's bath. The addition 
of sodium citrate to the extent of 35 gm. per liter gave a good 
deposit at a current density of 2 amperes, while only 1 amp. was 
required to secure a good deposit when 70 gm. per liter of sodium 
citrate were used. When the concentration of nickel sulphate was 
increased to 240 gm. per liter, the minimum current density for 
a good deposit was 5 amp. The addition of 70 gm. of sodium 
citrate per liter lowered the minimum current density for a good 
deposit to 3 amp., and as the citrate was increased, the current 
density required for a good deposit decreased, until, upon the 
addition of 175 gm. per liter, a bright deposit was secured at the 
low current density of 0.5 ampere. 

In Table XII the data show the effects of the separate addi- 
tions of progressively increasing amounts of sodium succinate, 
sodium malate, and sodium potassium tartrate on the character 
of the nickel deposits made directly on zinc. 



Table XII. 





Amp. 


CD. 


E. M. F. 
Volts 


Polar- 
ization 
Volts 


Deposit 


NiS04.6H=0 
NiCl=.6H20 
H,B03 
KNaC4H406.4H20 

NiS04.6H20 
NiC1..6H20 
H,B03 
KNaC4H406.4H20 


240 1 
10 , 
30 1 
35 J 

240 1 
10 I 
30 f 
70 J 


0.10 

0.20 
0.30 

0.10 

0.20 
0.30 
0.40 


1.00 

2.00 
3.00 

1.00 

2.00 
3.00 
4.00 


1.70 

2.20 
3.20 

1.90 

2.25 
3.60 
4.00 


0.5 

0.5 
0.5 

0.5 

0.5 
0.5 
0.5 


Bright with some brown 

streaks. 
Bright, white. 
Bright, white, edges slightly 

burned. 

Fine. Slight brown area 
at top of cathode. 

Brown areas, polished well. 

Matte. Polished well. 

Matte. Edges slightly 
burned. Polished well. 



120 



L. D. HAMMOND. 



Table XII (Continued). 





Amp 


C. D. 


E. M .F. 
Volts 


Polar- 
ization 
Volts 


Deposit 


NiS04.6H,0 


240 1 


0.05 


0.50 


1.45 


0.5 


Bright, adherent. 


NiCl2.6H20 


10 ! 
30 f 


0.10 


1.00 


1.90 


0.5 


Matte. Polished well. 


H.BO3 


0.20 


2.00 


3.00 


0.5 


Burned, unsatisfactory. 


KNaC4H.O6.4H2O 105 J 


0.20 


2.00 


3.00 


0.5 


Burned, unsatisfactory. 


NiS04.6H.O 


240 1 


0.05 


0.50 


1.50 


0.5 


Bright. Small brown areas. 


NiCU.6H.O 


10 ! 

30 r 


0.10 


1.00 


2.50 


0.5 


Bright, adherent. 


H.BO, 


0.20 


2.00 


3.00 


0.5 


Bright. Edges rough. 


KNaCH.O«.4H.O 140 J 


0.30 


3.00 


3.50 


0.5 


Rough, unsatisfactory. 






0.05 


0.50 


1.55 


0.5 


Yellow, brown streaks, pol- 
ished well. 






0.10 


1.00 


2.70 


0.5 


Yellow, brown streaks, pol- 


NiS0..6H.O 


240 1 










ished well. 


NiC1..6H,0 

HsBO:, 


10 1 
30 f 


0.20 


2.00 


3.20 


0.5 


Slightly burned on edges, 
rough areas. 


KNaC4H40e.4H20 175 J 


0.30 


3.00 


3.60 


0.5 


Slight burned on edges. 














rough areas. 






0.40 


4.00 


4.15 


0.5 


Burned, unsatisfactory. 






0.05 


0.50 


1.20 


0.5 


Brown streaks. 


NiS04.6H.O 

Nicu.en^o 

H.BOa 


240 1 
10 1 
30 f 


0.10 
0.20 


1.00 
2.00 


1.50 
2.10 


0.5 
0.5 


Fine brown lines. 
Fine brown lines. 


0.30 


3.00 


2.55 


0.5 


Fine brown lines. 


Na.C4H,04.6H.O 


35 J 


0.40 


4.00 


3.00 


0.5 


so many. 
Better, but not satisfac- 
factory. 






0.05 


0.50 


1.20 


0.5 


Black. 


NiS04.6H.O 


240 1 


0.10 


1.00 


1.62 


0.5 


Brown lines. 


NiCl=.6H20 


10 
30 i 


0.20 


2.00 


2.10 


0.5 


Brown lines, but not so many. 


H.BO3 


0.30 


3.00 


2.70 


0.5 


Fine brown lines. 


Na.C4H.04.6H.O 


70 J 


0.40 


4.00 


2.88 


0.5 


Matte. Burned on edges. 






0.50 


5.00 


3.00 


0.5 


Matte. Burned on edges. 






0.05 


0.50 


1.10 


0.5 


Brown lines. 






0.10 


1.00 


1.45 


0.5 


Brown lines. 


NiS04.6H20 

NiCU.6H.O 

H.BO, 


240 ~1 
10 ' 
30 ( 


0.20 
0.30 


2.00 
3.00 


1.90 
2.15 


0.5 
0.5 


Few brown lines. Pol- 
ished well. 
Matte. Polished well. 


2Na2C4H405.H=0 


35 J 


0.40 


4.00 


2.60 


0.5 


Matte. Polished well. 






0.50 


5.00 


3.20 


0.5 


Matte. Polished well. 


NiS04.6H.O 


240 1 
10 1 


0.05 


0.50 


1.20 


0.5 


Brown lines. Non-adherent. 


NiCU.6H=0 


0.10 


1.00 


1.45 


0.5 


Matte. Polished well. 


H.BO. 


30 r 


0.20 


2.00 


1.95 


0.5 


Matte. Polished well. 


2NajC4H405.H20 


70 J 


3.30 


3.00 


2.50 


0.5 


Matte. Polished well. 


NiS04.6H20 

NiCU.6H.O 

H,BO. 


240 1 


0.05 


0.50 


1.20 


0.5 


Non-adherent. 


10 ! 
30 ( 


110 


1.00 


1.52 


0.5 


Matte. Polished well. 


3.20 


2.00 


2.10 


0.5 


Matte. Polished well. 


2Na2C4H40..H20 


105 J 











THE EI^KCTRODEPOSITION OF NICKEL. 121 

Table XII. — One hundred seventy-five grams per liter of potas- 
sium sodium tartrate can be added to a solution of 240 gm. per 
liter of nickel sulphate without producing a precipitate. The 
addition of 35 and of 70 gm. per liter of sodium succinate to a 
nickel sulphate solution of the same concentration produced a 
slight precipitate, which was removed. One hundred five grams 
per liter of sodium succinate produced such a copious precipitate 
as to render the bath unfit for use. The successive additions of 
sodium malate produced a slimy, green coating on the cathode. 
It has been shown that sodium citrate decreases the rate of depo- 
sition by immersion and the data in this table show that the addi- 
tion of sodium potassium tartrate and sodium malate to the nickel 
bath has the same effect. Sodium potassium tartrate to the extent 
of 105 gm. per liter will permit nickel to be deposited directly 
on zinc at a current density of 0.5 ampere per sq. dm., while 175 
gm. per liter of sodium citrate were required to produce the same 
result. On the other hand, the citrate bath can be successfully 
operated at a current density of 7 amp. per sq. dm., while 3 amp. 
per sq. dm. is the maximum current density for the tartrate bath. 
The addition of 70 gm. per liter of sodium malate produced a 
good deposit at a current density of 1 amp. per sq. dm. The 
cathode was always covered with a slimy green coating and it 
was impossible to obtain a good deposit at a current density lower 
than 1 amp. The addition of sodium succinate failed to produce 
a good deposit. It is of interest that the sodium or potassium 
salts of succinic acid do not produce a good deposit of nickel on 
zinc, while the same salts of malic acid (monohydroxy succinic 
acid) and tartaric acid (dihydroxy succinic acid) do produce good 
deposits. Furthermore, sodium citrate, which also produces a 
good deposit directly on zinc, is the sodium salt of hydroxytri- 
carballylic acid. These experiments show that the production of 
a good deposit of nickel directly on zinc is related in some way 
to the presence of the hydroxyl group. This matter is reserved 
for further inquiry. 

Thus it will be seen that, while either sodium potassium tar- 
trate or sodium malate can be substituted for sodium citrate in 
baths used for the direct nickeling of zinc, sodium citrate is to be 
preferred on account of its greater solubility and on account of 
the fact that it permits the use of a wider range or current den- 
sities. 



122 L. D. HAMMOND. 

Proctor*^ proposes the following bath for the direct nickeling 
of zinc: 

NiS04.(NH4)2SO,.6H.O 60 gm. 

NiS04.6H=0 IS " 

NH.Cl 15 " 

MgSO.-H^O 30 " 

H.BO. 7.5 " 

H.O 1000 cc. 

Anodes of rolled sheet steel were advised, with an E. M. F. of 
3.5 volts. Using electrolytic nickel anodes, a metallic, yellowish, 
adherent deposit was secured at a current density of 1 amp. and 
an E. M. F. of 1.35 volts. A bath was next prepared in which all 
ammonium salts were excluded, but the nickel, boric acid, and 
chloride contents were kept the same and the magnesium sulphate 
was retained. It had the following composition : 

NiS04.6H.O 55 gm. 

MgSO^.H.O 30 " 

H3BO3 7.5 " 

NiCU.eH^O 3.5 " 

H2O 1000 cc. 

Using a current density of 1 amp. at 3.65 volts the deposit was 
uneven with dark and yellow areas. Upon the addition of boric 
acid sufficient to increase its concentration to 30 gm. per liter, and 
electrolyzing under the same conditions, a fine deposit of yellowish 
tint resulted. The following electrolyte was then prepared : 

NiS0..6H=0 55 gm. 

NiCU.6H=0 10 " 

HsBOa 30 " 

H=0 1000 cc. 

From this bath, a fine, adherent deposit of yellowish nickel was 
obtained under the same electrolyzing conditions just mentioned. 
This shows that the magnesium sulphate plays no part in deter- 
mining the physical properties of the deposited metal. The fact, 
that in the absence of the ammonium salts an unsatisfactory 
deposit was obtained and that a good one resulted when the con- 
centration of boric acid was increased, shows that a good deposit 
can be secured only in the presence of some substance which will 

"Metal Industry, 13, 274 (1915). 



THE ELECTRODEPOSITION OF NICKEL. 1 23 

dissolve basic salts that precipitate on the cathode and spoil the 
deposit. In the first case ammonium salts dissolved the basic 
nickel salt that tended to precipitate, while in the second case this 
result was accomplished by boric acid. Thus is demonstrated the 
reason why in those baths containing no acid, the much-used nickel 
ammonium sulphate and ammonium chloride have been preferred 
to nickel chloride and the more soluble nickel sulphate. 

Owing to the more electro-positive nature of zinc, it is more 
difificult to deposit a good coating of nickel on this metal than on 
a more negative metal, such as copper, on account of the trouble 
caused by the deposition of nickel by immersion, which causes the 
electrolytic deposit to peel. It has therefore been thought neces- 
sary to add substances to the electrolyte to make the zinc less 
positive. Single potential measurements, however, show that the 
potential of the zinc has not been changed, and experiment has 
shown that these substances do not alter the character of the 
deposit. Zinc may be nickeled directly from the same bath used 
for copper or for brass, the only difference being in the current 
density which it is necessary to employ. Zinc requires a higher 
current density, especially at the beginning of the electrolysis, to 
coat the metal quickly with nickel so as to minimize deposition by 
immersion. The greater the concentration of nickel in the elec- 
trolyte, the greater must be the initial current density used. It 
has been found, however, that alkaline citrates, tartrates and 
malates reduce the initial current density necessary to be em- 
ployed with concentrated nickel solutions. 

An electrolyte of the following composition was prepared : 

NiS0..6H.O 120 gm, 

NiCU.6H.O 15 " 

H3BO3 30 " 

H=0 1000 cc. 

This bath may be used to give a deposit on zinc, copper, brass 
or iron. In order to deposit on copper, a current density varying 
from a few tenths of an ampere to three or four may be used, 
but to deposit on zinc, not less than 3 amp. can be employed, 
which will produce a coating of nickel on a piece of zinc in one- 
twelfth of the time required for Pfanhauser's bath. 

While excellent results were obtained from this bath when flat 
pieces of zinc in the form of strips were used, it is possible that. 



124 



L. D. HAMMOND. 



when zinc objects of irregular form are to be plated, black streaks 
may be formed on those parts of the object which may be sub- 
jected to a lower current density. In order to overcome this 
difficulty, the following new bath is proposed for the direct and 
rapid nickeling of zinc : 

NiSOi.eH^O 240 gm. 

NiCl2.6H.O 15 " 

H.BOs 30 " 

2Na.GH:,0:llH.O 175 " 

H .O 1000 cc. 

This bath has been operated at current densities varying from 
0.5 to 7 amperes per square decimeter and satisfactory deposits 
were secured. Pure electrolytic nickel anodes should be used. 

In all the baths for the direct nickeling of zinc there is a lack 
of acid, except in those proposed within the last few years, which 
contain boric acid. However, this is such a weak acid that there 
is no appreciable action on the zinc even on open circuit. It has 
been shown, however, that nickel can be deposited directly on zinc 
from electrolytes strongly acid in reaction. Not only have fairly 
concentrated solutions of organic acids been used, but the strong 
mineral acids also. Table XIII shows the efifect, on the character 
of the deposit, of progressive additions of 4N hydrochloric acid 
to an electrolyte of the following composition : 

NiS04.6H20 160 gm. 

NiCl2.6H=0 6 " 

H2O 1000 cc. 

This experiment was carried out with 250 cubic centimeters of 
the above electrolyte, to which the indicated volumes of the acid 
were added. 

Table XIII. 



cc. 4NHCI 
added 


Amp. 


C. D. 


E. M. F. 
Volts 


Polar. 
Volts 


Deposit 





2.00 


8.33 


10.00 


2.00 


Green, non-adherent. 


1 


2.00 


8.33 


10.00 


2.00 


" " " 


1 


1.00 


4.16 


9.00 


2.00 


" " " 


3 


0.74 


3.08 


8.00 


1.80 


" " " 


5 


0.84 


3.50 


8.00 


0.95 


" " " 


10 


1.00 


4.16 


8.00 


0.70 


Metallic, buffed off. 


5 


1.80 


7.50 


8.00 


0.70 


Metallic, yellow, stood buffing. 


5 


2.20 


9.16 


6.00 


0.60 


Bright, yellowish, adherent. 



THE ELECTRODEPOSITION OF NICKEL. 125 

Table XIII shows that with the successive additions of hydro- 
chloric acid, the passivity of the electrolytic nickel anode decreased, 
and the character of the deposit gradually improved until a satis- 
factory one was obtained after the addition of 25 c.c. of 4N 
hydrochloric acid. The acid content of the electrolyte was pro- 
gressively increased until it finally contained 17.52 gm. of HCl 
per liter. 

III. THE FUNCTION OF BORIC ACID. 

Edward Weston, of the Weston Electrical Instrument Co., of 
Newark, N. J., was the first to use boric acid in the nickel bath 
and he patented*^ its use in 1878. Since the expiration of the 
patent, its use has become very general in commercial plating. 
"He claims*"' that the addition of boric acid or its compounds 
prevents the deposition of sub-salts upon the cathode, renders the 
solutiofi more constant and stable in composition, diminishes the 
liability to the evolution of hydrogen, permits the use of a more 
intense current, and improves the character of the deposit by 
rendering it less brittle and by increasing the tenacity with which 
it will adhere to a metal surface." 

Langbein*® states that "the action of boric acid has not yet been 
scientifically explained, but numerous experiments have shown 
that the deposition of nickel from nickel solution containing boric 
acid is neither more adherent nor softer and more flexible th^n 
that from a solution containing small quantities of a free organic 
acid. Just the contrary, the deposition is harder and more brittle 
in the presence of boric acid * * * j^^ has a favorable effect 
upon the pure white reduction of the nickel, especially in ihe 
nickeling of rough castings." 

Bennett,*^ in discussing the paper of Kalmus on the electro- 
deposition of cobalt, says, "The solution of cobalt sulphate, which 
contains only a little greater quantity of cobalt, can be run at 
much higher rates of deposition in the presence of sodium chloride 
and boric acid. Since it seems to be impossible to get the people 
who are interested in nickel plating to explain the effect of such 
additions, it appears to me that Mr. Kalmus would advance our 

"U. S. Patent, 211071, Dec. 17. 1878. 

« Watts, Trans. Amer. Electrochem. Soc, 23, 132 (1913). 

*« Electro-deposition of Metals (1909), p. 249. 

■•'Trans. Amer. Electrochem. Soc, 27, 118 (1915). 



126 L. D. HAMMOND. 

knowledge of electro-deposition, and, furthermore, score heavily 
on the nickel people, if he would determine what the specific action 
of boric acid and sodium chloride is." 

Quite recently the Brass World^^ published an article by E. S. 
Thompson, purporting to give an explanation of the function of 
boric acid. That the article was written by one who is evidently 
unacquainted with even the rudiments of chemistry and electricity 
is shown by the following excerpt : "We will consider a solution 
composed of nickel sulphate, sodium chloride and boric acid. As 
the electric element forces oxygen out at the anode it necessarily 
forms a new combination with the hydrogen, and perhaps the 
nickel. But as we have boric acid there as a catalytic agent, it 
takes charge of the electric current and forms a combination with- 
out itself undergoing decomposition, and forces the sulphuric acid 
out of its combination with nickel. The chlorine which has been 
forced out of the sodium rushes in to take the place of the boric 
acid and forms chloride of nickel, having electro-hydrogen (we 
will call it that) as its solvent. * * * "fht oxygen is forced 
out of the solution at the anode, its volume being exactly equal 
to the volume of electricity which has entered the solution. Then 
the boric acid takes charge of the electricity for an instant and 
forms a combination with the nickel sulphate. * * *. It will 
be seen by this that the handling of these solutions must be done 
by a man who understands their actions." 

Having succeeded in securing satisfactory deposits of nickel 
from electrolytes containing small concentrations of the inorganic 
and organic acids, it seemed probable that the action of boric acid 
was simply to maintain a faint acid reaction in the electrolyte, 
which is a condition essential to a good deposition of nickel. The 
data which support this view are given as follows : 

A bath consisting of 120 gm. per liter of nickel sulphate was 
prepared, neutralized with nickel carbonate and "aged" for 24 
hours at a low current density. This solution was neutral to lit- 
mus. Using a copper cathode, current densities from 0.6 amp. to 
3 amp. per sq. dm. were employed, but a satisfactory deposit was 
not obtained. At the lower current densities the deposit was black 
and rubbed oflf, while at the higher current strengths there was a 
coating on the cathode of a salt of a light green color. However, 

"Brass World, 12, 37 (1916). 



THE SI^ECTRODEPOSITION OF NICK^I.. 127 

a bright, adherent deposit was obtained upon the addition of 0.25 
percent of sulphuric acid. 

Again, an electrolyte was prepared which had the following 
composition : 

NiSO,.6H20 120 gm. 

NiCl2.6H20 10 " 

K2SO 2.5 " 

H2O 1000 cc. 

Upon electrolyzing at various current strengths with a copper 
cathode no satisfactory deposit was obtained. Another electro- 
lyte was prepared of similar composition except that potassium 
hydrogen sulphate was substituted for the normal salt, and fine, 
bright, adherent deposits were obtained at current densities of 0.5 
amp. and 1 amp. per sq. dm. Higher current densities gave 
unsatisfactory deposits. 

A bath was made by digesting a saturated boric acid solution 
with nickel carbonate until the resulting solution was neutral to 
litmus. Electrolyzing at three different current strengths, the 
deposits were all dull gray and non-adherent, but upon adding 
boric acid to a concentration of 30 gm. per liter, a fine metallic, 
adherent deposit resulted. Again a solution containing 120 gm. 
per liter of nickel acetate failed to give a good deposit, but upon 
acidifying with 0.25 percent of glacial acetic acid, a fine, metallic, 
adherent deposit was obtained. Likewise, an electrolyte consisting 
of" 120 gm. of nickel chloride per liter gave deposits which were 
black and non-adherent, but upon the addition of 9 cc. of 4N 
hydrochloric acid, a bright, adherent deposit was produced. 
Neutral potassium tartrate added to a solution of nickel sulphate 
does not cause a good deposit, but the addition of potassium 
hydrogen tartrate gives a fine deposit. 

A solution consisting of 120 gm. of nickel sulphate and 10 gm. 
of nickel chloride per liter was prepared, but it failed to give a 
good deposit at several different current densities. This solution 
was then acidified separately with sulphuric, boric, acetic, lactic, 
nitric, phosphoric, oxalic, tartaric, citric, succinic, benzoic, sali- 
cylic and hydrochloric acids. From each different bath a good 
deposit was obtained. In the case of the benzoic and salicylic 
acids the solutions were prepared by adding the required amount 



128 Iv. D. HAMMOND. 

of nickel sulphate to water saturated with respect, to the acid at 
room temperature. Indeed, in so far as the electrolyte is con- 
cerned, a nickel sulphate solution acidified with hydrochloric acid 
contains all the factors necessary for a good nickel deposit. There 
is chloride to insure good anode corrosion, and acid to promote 
a bright, adherent deposit. In fact, such a solution gave fine, 
adherent deposits at current densities varying from 0.7 amp. to 
2 amp. per sq. dm. 

The results of these experiments are very interesting. An acid 
reaction to the electrolyte is necessary for a good deposit of 
nickel, since those baths which were neutral in reaction all failed 
to give a good deposit. Since good deposits were secured from 
solutions acidified separately with sulphuric, boric, lactic, acetic, 
nitric, phosphoric, oxalic, tartaric, citric, succinic, benzoic, salicylic 
and hydrochloric acids, it is demonstrated that boric acid has no 
function in the electrolyte which is different from that of any 
other acid. It simply maintains in the electrolyte a small concen- 
tration of acid, which is necessary to secure a good deposit. Owing 
to the fact that it is fairly soluble, and to the fact that it is a very 
weak acid, it lends itself to practical use better than most of the 
acids listed above. To show how weak boric acid is, it is only 
necessary to recall the well-known fact that a solution saturated 
with boric acid at room temperature may be dropped into the eye 
with impunity. Boric acid, then, simply acts in the capacity of a 
reservoir for keeping up a constant but small concentration of 
hydrogen ions in the electrolyte. In so far as their effect on the 
properties of the deposited nickel is concerned, hydrochloric or 
sulphuric acid could be substituted for the boric acid, but since 
the hydrogen ions in the electrolyte are gradually plated out, these 
strong acids, at the concentrations which must be employed, are 
already completely ionized and so cannot furnish more hydrogen 
ions to the electrolyte as the very weak boric acid can do. In this 
fact lies the only difference in the function of boric, sulphuric or 
hydrochloric acids in the plating bath, except that, in the case of 
hydrochloric acid, the chloride increases anode corrosion. 

In a recent paper, Mathers*'' has recommended a nickel bath 
of the following composition : 

"Trans. Amer. Electrochem. Soc., 29, 383 (1916). 



the; electrodeposition of nickel. 129 

NiS04. (NH4)2S04.6H20 40 gm. 

NiS0..6H.O 120 " 

H3BO. 20 " 

MgCU.eHsO 20 " 

(NHOsCeHaOr 3 " 

H2O 1000 cc. 

The maximum current density that could be used was 1.6 amp. 
per sq. dm. It seems that this bath is more complex than neces- 
sary. Better conductivity is obtained by adding nickel ammonium 
sulphate, but this results in a lowered nickel content, which does 
not permit the bath to be operated at a current density higher 
than 1.6 amp. Magnesium chloride insures proper anode corro- 
sion, but it would be better to substitute nickel chloride for this 
purpose in order not to decrease the nickel content. Ammonium 
citrate is added to prevent the formation of basic compounds from 
iron in the so-called "soft" anodes, but when chloride is present, 
it is unnecessary to employ such anodes, as pure nickel anodes 
would corrode properly. 

For general purposes a bath of the following composition is 
proposed : 

NiS04.6H=0 240 gm. 

NiCU.eH.O 15 " 

H.BO3 30 " 

H2O 1000 cc. 

These salts are readily soluble at ordinary temperature and the 
boric acid may be readily dissolved by raising the temperature of 
the water slightly, although the acid will dissolve at room tem- 
perature. At this temperature the bath may be operated at any 
current strength between 0.5 amp. and 10 amp. per sq. dm., and 
by raising its temperature to 75°, it is possible to employ current 
densities as high as 33 amp. per sq. dm., as Watts^° has recently 
demonstrated. At room temperature the specific resistance of 
this electrolyte is 23.54 ohms per centimeter cube, while that of 
Mathers' bath is 24.56 ohms. 

In the same paper Mathers^^ states that "citric, acetic or benzoic 
acids cannot be used in the place of boric acid." If this statement 
means that good deposits of nickel cannot be obtained from 
electrolytes acidified with these acids, then the writer cannot 

™ Trans. Amer. Electrochem. Soc, 29, 395 (1916). 
"Trans. Amer. Electrochem. Soc., 29, 383 (1916). 

9 



130 L. D. HAMMOND. 

concur in it, as excellent deposits were obtained from baths acid- 
ified separately with all these acids as well as with salicylic acid. 
At first, trouble was experienced in getting an adherent deposit 
from the benzoic acid bath, but the trouble was traced to the fact 
that the copper cathode was being subjected too long to the action 
of the electric cleaner. When it was allowed to stay in the cleaner 
for about ten seconds, a bright, adherent deposit was obtained 
from the benzoic acid bath. 

Bennett^- states that "nickel cannot be deposited from an acid 
solution," and later explains that although the body of the electro- 
lyte may be acid in reaction, yet to secure a good deposit the film 
of solution next to the cathode must be alkaline. He further ex- 
plains that the hydrogen liberated during the electrolysis of an 
acid solution "leaves the hydroxy! ion from the water in slight 
excess at the cathode." The concentration of hydroxyl ions that 
serves to maintain equilibrium conditions in water is, at best, very 
small, and when this very small concentration of hydroxyl ions 
is further reduced by the addition of a strong acid, such as hydro- 
chloric or sulphuric, it is hard to believe, from theoretical con- 
siderations, that the minutely small concentration of hydroxyl 
ions, which maintains equilibrium conditions, could play any im- 
portant part in causing a good deposition of nickel. Thus, from 
theoretical considerations, the hypothesis that a film of electrolyte, 
alkaline in reaction next to the cathode, is a condition necessary 
to secure a good deposit of nickel is untenable and, practically, 
it is well known that the electrolyte must be slightly acid in re- 
action to secure the same result. 

SUMMARY. 

1. A study of the corrosion of cast nickel, electrolytic nickel, 
and annealed electrolytic nickel anodes has been made in the fol- 
lowing electrolytes : nickel sulphate solution ; nickel sulphate solu- 
tion to which boric acid was added; nickel sulphate boric acid 
solution to which various amounts of nickel chloride were added. 

2. Measurements of the total polarization pressures and cur- 
rent efficiency tests of these three anodes in the electrolytes listed 
above have been made. 

"Trans. Amer. Electrochem. Soc, 25, 338 (1914) . 



THE ELECTRODEPOSITION OF NICKEL. 131 

3. A study has been made of the conditions necessary for the 
direct electro-deposition of nickel on zinc, together with some of 
the electrolytes which have been proposed for this purpose. 

4. Nickel can be deposited directly on zinc from baths used to 
deposit nickel on more electro-negative metals by employing a 
higher initial current density than is used with the more electro- 
negative metals. 

5. Nickel has been deposited directly on zinc from an approxi- 
mately half normal hydrochloric acid solution to which 120 gm. 
per liter of nickel sulphate were added. 

6. The beneficial action of sodium citrate in the baths for the 
direct nickeling of zinc has been found to consist not in changing 
the potential of zinc but in decreasing the rate of deposition by 
immersion. Sodium potassium tartrate and sodium malate have 
a similar action but they do not permit the use of as high a current 
density as the citrate bath. 

7. A new bath for the rapid and direct nickeling of zinc is 
proposed. 

8. The use of pure nickel anodes and the use of nickel chloride 
to secure anode corrosion, instead of any other chloride, is advo- 
cated. 

9. The use of nickel sulphate in the electrolyte instead of 
nickel ammonium sulphate is advocated. 

10. The function of boric acid in the electrolyte has been ex- 
plained. 

In conclusion, the writer desires to express his appreciation of 
the assistance given him by Dr. O. P. Watts during the progress 
of the work reported in this paper. 

Laboratory of Applied Electrochemistry, 

University of Wisconsin, 

May, 1916. 



DISCUSSION. 



G. B. HoGABOOM : I would like to speak upon this paper, pri- 
marily in the way of making a plea for the members of the 
American Electro-platers Society. The author in the first para- 
graph acknowledges that nickel plating is not practiced by those 



132 DISCUSSION. 

who are thoroughly famiHar with the fundamental principles of 
chemistry and electricity, and then writes a paper in the most 
technical terms. 

This is a paper for the electro-chemist, and loses a great deal 
of its value to the nickel-plating industry on account of its highly 
technical character and because all of the measurements are given 
in the metric system. 

The author makes the statement in the paper that although 
nickel plating has been practiced for about fifty years, it is still 
based upon "cut and dried" methods. That puts me in mind of 
Elijah when he said that he "alone was left to represent the chil- 
dren who worshipped and feared God" ; because if he had looked 
around he would have seen that there are a great number of the 
larger plants which are carrying on nickel plating on scientific 
principles, and the art is progressing very well along that line. 

On page 107, speaking about the presence of iron, tin and 
carbon in the solution, he says : "Although solution of anode is 
promoted by such a practice, serious troubles result." I have seen 
solutions that have been in use for twenty-five years and were 
still being used, without any serious trouble following. In prac- 
tice this statement is disproved. 

If the author was familiar at all with the nickel deposits, he 
would know that a small percentage of copper in nickel will cause 
a black deposit. 

I had occasion to look over some deposits of nickel on highly 
polished steel that were peeling, the solution was quite acid from 
the addition of an excess of boric acid. A nickel deposit that 
peels on account of it being acid from sulphuric acid, if crushed 
in the hand, will cry like tin. A deposit that peels from boric 
acid will crumble up in your hand and will not cry at all. 

Leonard Waldo: I note one thing on page 126, an article 
published in the "Brass World" is very sharply criticised. I notice 
the edition of the "Brass World" in which the criticism occurs is 
the twelfth volume, 37 something, in the year 1916. The paper 
proceeds to criticise the article which was published in the "Brass 
World," and I attribute the inaccuracy of the "Brass World," in 
this instance, to the decease of that brilliant brass and copper 
metallurgist, Irwin Starr Sperry, its former editor. 



THE ELECTRODEPOSITION OF NICKEE. 133 

C. G. Fink : It is gratifying to hear that the "Brass World" has 
taken the lead in using both systems of measurements, and I hope 
the "Metal Industry" will soon follow suit. I wonder whether 
our Society could not induce the "Metal Industry" to adopt the 
metric system at least partially, adding the metric system in paren- 
thesis with the present English system. This procedure would 
make it so much easier for the chemist, who is not a plater, to 
read the plater's article. It is more difficult to comprehend 
"ounces of silver per barrel" than "grams per litre." 

L. D. Hammond {Communicated) : Mr. Hogaboom is quite 
correct in his statement that this is a paper for the electro-chemist, 
but it is to be regretted that the only thing he got out of it was 
the impression that I had set myself up as an Elijah. In this 
connection, however, it may be well for him to recall that it was 
Elijah who pointed out to his people the mistakes they were 
making, and that Elijah's work was constructive. Experience 
has shown that the plater is not independent of his scientifically 
trained brother, and the electro-chemist has much to gain from 
the helpful suggestions of his more practical brother. The chasm 
that separates the practical man from the theoretical one must 
be bridged by the real Elijah of the situation, who will be the 
college-trained man with an apprenticeship in the practical field. 
Such a man would interpret to workers in the practical field any- 
thing of interest and value to them in a technical paper instead 
of dismissing it with the statement that the author assumes unto 
himself the role of an Elijah. The electro-chemist and electro- 
plater must work hand in hand and it is to be regretted that my 
paper was interpreted in any other way by the representative of 
the platers. 

Mr. Hogaboom asserts that he knows of plating solutions which 
have been used for twenty-five years without any serious trouble 
following. It seems to me he is looking at the problem from the 
standpoint of the practical man who is interested only in securing 
a good deposit on the article to be plated. But what of the effi- 
ciency of anode corrosion, and what of the efficiency of depo- 
sition at the cathode? Did the article show signs of rusting 
sooner or later from the iron deposited along with the nickel? 
These are questions which must be considered as well as the char- 
acter of the deposit. 



134 DISCUSSION. 

As to Mr, Hogaboom's reference to the effect of a small per- 
centage of copper in nickel deposits, his remarks are entirely 
gratuitous so far as my paper is concerned, as the only statement 
I made in regard to this matter was to quote others, including 
Mr. Hogaboom himself. 

I was pleased to receive from Mr. Waldo an explanation as to 
why that article on the function of boric acid in the nickel bath 
was ever published in the "Brass World." The editorship of the 
trade journals is another field requiring the services of the new 
Elijah — the college man with a practical training. 

In view of Mr. Hogaboom's criticism that all the measurements 
are given in the metric system, it is interesting to learn from Mr. 
Fink that the "Brass World" is doing pioneer work in introducing 
into its columns the use of the metric system, and to learn, as well, 
that he hopes the "Metal Industry" may be induced to do hkewise. 
It is hard to break away from a long-established habit, but the 
universal use of the metric system is coming, and the wise prac- 
tical man will prepare himself accordingly. And once he becomes 
accustomed to its use I imagine he will often wonder why we 
have endured our present cumbersome system of weights and 
measures so long as we have. 



LIBRARY OF CONGRESS 



lllillll Hill III 
014 633 369 2 



